Known in the art is a method of correction ocular refraction anomalies which comprises supplying of pulsed ultraviolet radiation with a wavelength of 193 nm on the cornea surface and evaporation of the cornea in layers until obtaining required correction of refraction anomalies. (Lasers in Ophthalmology, vol. I, N1, 1986, Amsterdam, J. Marshall, S. Trakel, S. Rothery, R. R. Krueger "Photoablative" reprofiling of the cornea using an eximer laser. Photorefractive keratectomy, p. 21).
The speed of evaporation of the cornea at said wavelength of radiation is negligible which calls for a greater number of pulses fed. And since the human eye is a live object, any delay in operation can lead to the loss of accuracy.
Known in the art is a method for treating myopia, which comprises evaporation of the cornea in layers, using pulsed ultraviolet radiation with a wavelength of 193 nm through a rotating slotted mask. With due regard for losses in the optical system from a laser energy of 167 mJ it is mere 4.5 mJ that gets to the surface of the cornea with a density of 200 mJ/cm.sup.2 which exceeds the threshold value for the cornea ablation by a factor of two. What is optimal, however, is a higher range of energy densities so that without increasing the degree of thermal corneal injury to attain maximum rate of the tissue ablation. For this purpose, there is needed a laser with a radiation energy of 334-835 mJ at a wavelength of 193 nm, which in addition to technical difficulties of developing the laser per se has a great energy consumed and large overall dimensions, which may be reflected on the conditions of arranging the apparatus in the operation room (K. Hanna, J. C. Chastang, Y. Pouliquen, G. Renard and L. Asfar, Excimer Laser Refractive Keratoplasty, Paris, 1986, p. 1, 3).
It is worthy of note that the human eye is a movable object and can be constructed and displaced in the period of pulsed influence which impairs the accuracy of correction and is likely to cause astigmatism.
A known device for performing ophthalmologic operations by a photoevaporation method comprises a solidstate laser having an operating wavelength of 150 to 220 nm and such optically interconnected components as a controlled shutter, an optical section, an electric or acoustic modulator and a radiation wavelength converter (cf. PCT WO 87/00748).
Optical facilities of such a device are difficult to manufacture and control. The foregoing device calls for additional wavelength conversion and ensures point treatment of the corneal surface, which generally involves a complicated time-consuming procedure in obtaining a desired profile since the number of transmitted pulses is fairly great.
There is also known a device comprising an ultraviolet pulsed laser having an operating wavelength of 193 nm and such optically interconnected components as a uniform light beam former, a slotted mask having one slot shaped as a lobe, and a means for forming the mask image on the surface of the cornea. The slotted mask is provided with a drive enabling its rotation, a feature providing for axisymmetric distribution of radiation over the exposed surface of the cornea.
The disclosed device also comprises a microscope used to observe the emission of radiation to the surface of the cornea and the correction process, said microscope being optically connected with the image former, and a unit designed to monitor energy density of radiation incident on the surface of the cornea and arranged at the optical outlet of the image former (cf. K. Hanna, Jc. Chastang, J. Pouliquen, G. Renard, Z. Asfar: "Exciter laser refractive keratoplasty", 1986, Paris, p. 1).
The provision of one slot in the slotted mask does not permit increasing the correction speed since the pulse recurrence rate is positively limited by a cumulative thermal effect, a disadvantage increasing traumatism of biologic tissue.